Download Troubleshooting Propane Mowers

Backfiring
Liquid Slugging
1. B
ackfiring may be caused
by a mechanical problem
with a valve or rocker arm. Check them.
2. Backfiring may also be
due to an overheated
spark plug caused by an
improperly adjusted airfuel mixture. Check and
adjust the mixture.
3. Backfiring at idle may be
due to mechanical failure.
4. Backfiring under load
may be caused by an
overheated or worn spark
plug.
5. Backfiring through
the intake valve is not
common. It is usually caused by a failed rocker arm or
push rod.
6. Backfiring during deceleration is due to an over-rich fuel
mixture from a clogged air filter. Check the filter and
service as needed.
1. S
lugging only occurs in vapor fuel systems. If a mower is
operated on an extreme incline, liquid fuel may enter the
regulator from the vapor withdrawal tube.
2. Check that the fuel cylinder is a vapor-service cylinder.
3. Check the orientation of the fuel cylinder (locator pin in
neck ring locator hole).
4. If a strong odor of propane exists, the pressure regulator
may be frosted. This is a strong indication of liquid
slugging.
5. If slugging occurs, shut off the mower, close the cylinder
service valve, and allow the fuel to dissipate.
and
Propane Odor
1. If the operator smells propane, there is a leak. Propane
smells the same as natural gas, because the same
odorant compound is added to both fuels.
2. Close the cylinder service valve and check for leaks.
3. Use a propane leak detector or an approved liquid leakcheck solution that acts like a soapy water solution. 4. If odor is present at all times, check the cylinder, valves
and connectors for leaks. If odor is present only while
engine is running, then the regulator diaphragm is
defective. Rebuild or replace the regulator.
5. If the cylinder service valve is defective, have a propane
supplier check the valve, pump down the cylinder and
replace. Do not try to replace the valve due to the
pressure in the cylinder (typically 100-200 psi). Do not
try to transfer the fuel to another cylinder. Your propane
supplier has special equipment to evacuate a cylinder.
introduction to
propane-fueled
mowers
6. If so equipped, check the hydraulic lines to the vaporizer
for the correct connection.
7. If the fuel cylinder is the correct type and slugging
persists, substitute a fuel cylinder that is known to be
good and re-check operation.
For More Information
Propane Safety: www.propanesafety.com
National Standards: National Fire Protection
Association 58, Liquefied Petroleum Gas Code,
2011 ed. (NFPA 58). Chapters 5 and 11 cover
component specifications and engine-fuel
applications. To view or order copies, visit
www.nfpa.org.
State and Local Codes: State and local laws may
exceed or supersede NFPA standards. Contact
the authority having jurisdiction in your area for
requirements applicable to propane or propanefueled equipment.
troubleshooting
propane-fueled
mowers
introduction to
propane-fueled mowers
Propane Conversion
Engine Quits
Key Differences From a Gasoline Mower
•
he propane fuel supply must be turned on when the
T
mower is started and turned off when it is shut down,
using a manual valve on the cylinder.
• Propane is stored as a liquid under moderate pressure
(100-200 psi). The propane fuel cylinder is a sealed
pressure vessel that must match the type of fuel system
(vapor or liquid service) installed on the mower.
• Propane vapor fuel systems include an electrical lockoff,
a pressure regulator, and a propane mixer that replaces
the gasoline carburetor. All components of a propane
fuel system are propane-specific and must be approved
for use with propane.
1. D
isconnect the mower’s electrical system.
2. Remove the gasoline tanks, fuel lines, air filter assembly,
fuel pump, throttle, fuel filter and carburetor. 3. Retain the gasoline tanks if they are to be used for
mounting mower controls.
4. Pre-assemble the propane regulator, fuel line connections
and mixer according to the manufacturer’s instructions.
5. Install the regulator on the chassis.
6. Install the mixer and air-filter assembly on the engine.
7. Mount the fuel-supply cylinder securely on the chassis
with the locator pin in the hole on the neck ring to ensure
correct orientation. 6. If you are approved by U.S. DOT to re-qualify cylinders,
follow DOT procedures and recordkeeping requirements. Remove the cylinder from the mower, inform the owner
and record the cylinder serial number and date.
7. Inspect fuel lines for damage (UV deterioration, abrasion,
oil soaking). Route lines away from sharp edges, moving
parts and hot surfaces.
8. Heating hoses (if equipped) – inspect for leaks and
proper routing. Replace any damaged hoses or hose
clamps.
Troubleshooting a
Propane Mower
No Start
Propane System Inspection
Components of a Propane Vapor
Fuel System
Vapor Fuel Supply
Cylinder
Pressure
Regulator
High-Pressure
Hose
Low-Pressure
Fuel Line
Fuel Lockoff
Propane Mixer
(Carburetor)
1. A
n engine that quits lacks either air, fuel or spark.
2. Lack of air: Disassemble air filter; inspect and clean.
3. Lack of fuel: Check
fuel lockoff. The
lockoff is wired in
series with the chassis
safety switches.
4. Check fuel filter (if
present). Propane
can pick up red rust
from storage tanks
that can plug a filter.
5. Lack of spark: Ignition
failure is typically not
due to propane fuel. Check the engine manufacturer’s
service manual.
Overheating
1. O
verheating is usually not fuel-related.
2. Check for lawn debris blocking cooling fins. Check for
damaged cooling shroud or damaged fan.
3. Use compressed air (not a power wash) to clean the
engine, approximately every 100 hours.
4. In rare cases, overheating may be due to an air-fuel
mixture that is significantly out of adjustment. Usually
this condition is associated with a strong exhaust odor
and poor performance. Adjust the air-fuel mixture and
repair or replace the regulator, if possible. Most air-fuel
mixtures are not adjustable.
5. If so equipped, check the maximum gas flow control to
see if it has become loose or gone out of adjustment.
Misfiring
1. Check
cylinder type—vapor or liquid service. Vapor and
liquid service cylinders are not interchangeable.
2. Inspect the cylinder for damage.
3. Check cylinder position—locator pin in hole on neck ring.
4. Check cylinder mounting—cylinder secured firmly in
place. If the straps are broken, replace them. 5. Check cylinder requalification date. If the month and year
on the cylinder is more than 12 years earlier than the
current month and year, replace or requalify the cylinder.
1. C
heck for fuel in the cylinder by opening the fixed liquid
level gauge.
2. Check that the fuel lockoff is energized and the ground
wire is connected.
3. Check the pressure regulator for failed internal parts. Remove regulator and disassemble on a bench; inspect
the internal valves and seats. Repair or replace as
necessary. If the regulator is tamper-proof, replace the
regulator assembly.
Loss of Power
1. C
heck that the engine can rev to full speed with no load. Adjust throttle cable if necessary.
2. Apply a light load to see if the engine can power up to
full speed. If it can’t, check the air filter.
3. Check the maximum gas flow control on systems that
are so equipped. If provided, adjust for proper fullthrottle power and emissions.
1. M
isfiring is typically caused
by an ignition fault.
2. Check the spark plug, spark
plug wire, and ignition coil.
3. Check the vapor hose to
the mixer (carburetor) for
cracks.
4. If misfiring occurs at
idle, then check the
air-fuel mixture. If adjustable, adjust according to the
manufacturer’s specifications.
5. If the unit has a sealed mixture control with tamper-proof
screws, then replace the regulator.
continuted on back 